The present invention relates to a linear slide bearing which is widely employed in the sliding part of various general industrial machines such as X-, Y- and Z-axes of numerically controlled machine tools, automatic tool changers, automatic welding machines, injection molding machines and industrial robots, for example, a movable table for guiding a linear reciprocative motion.
The inventor of the present invention has previously proposed linear slide bearings of this type in Japanese Patent Application Nos. 49,170/1982 and 162,113/1982, which have not yet been laid open. These linear slide bearings are of so-called cantilever type wherein a pair of bearings are usually incorporated in a movable table, for example, and are adapted to guide a linear reciprocative motion along a track rail while bearing downward and horizontal loads by one of the skirts of the bearing case of each bearing which has a substantially C-shaped cross-section and upward and horizontal loads by the other skirt.
The previously proposed linear slide bearings have the following advantages: Since it is only necessary to provide a minimum number of loaded ball grooves on the bearing case and ball-rolling grooves on the track rail, which loaded ball grooves are required to have high accuracy in order to allow balls bearing a load to roll smoothly therethrough and consequently need a large number of steps in groove-grinding operation, it is possible to manufacture the bearings at a correspondingly low cost. Moreover, the bearings are easily incorporated in, for example, movable tables. In addition, the bearings are easily preloaded.
The above-described linear slide bearings, however, still inconveniently require the groove-grinding operation when forming two loaded ball grooves on the bearing case. Moreover, these loaded ball grooves are not easily machined, since they are located on the respective inner surfaces of both skirts of the bearing case. In addition, there is a need for an inconveniently large amount of labor in order to finish the loaded ball groove with high accuracy, particularly in the case where the loaded ball grooves need to be subjected to a so-called crowning operation wherein the groove width at both end portions of each loaded ball groove is made slightly larger than that at the central portion thereof, thereby to allow the balls to smoothly roll and recirculate from a non-loaded region to a loaded region and vice versa. In addition, it is necessary to form the whole of the bearing case from a material which is high in rigidity in order to cope with the requisite high rigidity for the portions of the bearing cases where the loaded ball grooves are to be formed. In consequence, although it is possible to minimize the number of the loaded ball grooves on the bearing case and the ball-rolling grooves on the track rail, the above-described linear slide bearings still suffer the problem of high production cost.